GNGTS 2014 - Atti del 33° Convegno Nazionale

a sustainable management of it, considering also the considerable water volumes required for the productive cycle of many crops. The method of Food and Agriculture Organization of the United Nations (FAO) for estimating crop water requirements, is based on the calculation of the crop evapotranspiration Etc as the product between the reference evapotranspiration (ET0) and the crop coefficient (Kc); where the evapotranspiration ET0 is defined as the loss of water due to the simultaneous processes of evaporation from the soil surface (E) and transpiration by the vegetation cover (T); while the crop coefficient Kc is a measure of the vegetative development of a specific crop in the various phenological phases (Allen et al ., 1998). Sensors for soil moisture estimation, as time domain reflectometry (TDR), can be used for verifying ET model applied in a given environments and for a given crop (Jeffrey, 2004; Thompson et al ., 2007). In addition, the structural complexity of the soil has suggested the implementation of integrated geophysical investigations as Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) in order to gain information about the soil moisture content. In fact, the integration of ERT and GPR reduces the ambiguity in the data interpretation by means of a suitable integrated survey design and data processing. In particular, the data obtained from these geophysical surveys provides information with very high detail about the soil layers and this allows at monitoring undesired water losses for percolation into the deeper layers. In this way, it is possible to design a proper scheduling of the amount of irrigation water for a particular crop, which is not based on the only information about the estimated evapotranspiration. In some research, geophysical measurements to spatial and temporal monitoring of soil water on irrigated crop were applied (Parchomchuk et al ., 1997; Michot et al ., 2003; Dahlin et al. , 2006; Pardossi et al ., 2009; Kelly et al ., 2011), and it appears that these geophysical measurements give a contribution on water irrigation management, moreover the measurements with integrated geophysical techniques have the advantage of being noninvasive, rapid and reproducible. A local population of dry bean (Phaseolus vulgaris L) named “fagiolo rosso scritto” has been cultivated at the Experimental Agricultural Farm “Pantano of Pignola” (40°33’31.34”N and 15°45’31.66”E); the farm is a facility of ALSIA (Agency for the Agricultural Development and Innovation of Lucania), Basilicata Region (Italy). Drip irrigation is a common practice worldwide, which compared to furrow or sprinkler irrigation, reduces deep percolation and evaporation and permits a more accurate control of the water within the crop root zone (Simsek et al. , 2011).The drip irrigation system was installed after sowing and placed at each row with drippers spaced every 20 cm apart and delivering 2.1 L/h. The drip lines ran along the 25 m of the rows and were 1.5 m spaced each other. The present paper illustrates the preliminary results of the integration of geophysical applications on a specific dry bean crop, for monitoring the water content in the soil and its distribution. Geophysical investigation. Eight waveguides long 20 cm were installed vertically along bean rows and distributed so to measure the average soil moisture in the depth profile 0-40 cm, corresponding basically to zone where the crop roots were present. During the growing season, a multiplexing time domain reflectometry system (TRASE, Soilmoisture Equipment Corp., California, USA) was deployed for a real-time monitoring of soil moisture content; the system was remotely controlled by a computer connected to internet network. TDR provides an indirect measurement of the soil water content by measuring the travel time that the guided electromagnetic wave employs to propagate through the thickness L of the soil to be reflected at the end of probe and to return to the TDR probe. As well known, the velocity v of the electromagnetic wave is inversely proportional to the square root of the soil apparent dielectric constant Ka , and because the soil is composed by solid particles ( Ka =3-5), air ( Ka =1) and water ( Ka =81), Ka varies significantly with soil volumetric water content. In particular, the relationship between Ka and soil water content is described using a calibration curve, which was established empirically by Topp et al. (1980). Field calibration of TDR system was performed with the gravimetric method; soil samples of known volume, using a metal cylinder sampler, were taken in the 0-40 cm soil depth range and heated at 105 degree centigrade for 72 hours, 228 GNGTS 2014 S essione 3.3